1. Field of the Invention
This invention relates generally to computer software and, more particularly, to a method and an apparatus for enabling an on-chip clock system to change frequencies as rapidly as needed.
2. Description of the Related Art
Computers typically have a timebase upon which the computers base their internal timing. Computers frequently find that the computers are idle. During such idle times, the computers often desire to decrease their power consumption.
Some conventional computers reduce their power consumption by slowing down their external timebases. Many clock chips support the changing of their output period under computer control in a safe way. One example of a conventional clock chip that supports the changing of its output period under computer control in a safe way is the Cypress CY2291.
However, such off-chip clock generators can typically vary their output frequency only slowly to reduce system power. Because of the requirements imposed on this sort of clock chip by the phase locked loops (PLLs), which can only use slowly varying clocks, in central processing units (CPUs), external clock chips cannot hop from one operating frequency to another operating frequency quickly. Such external or off-chip clock generators cannot be used when a central processing unit (CPU) needs to jump from sleep or idle mode to full speed quickly.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.